Ideas for Biamp with mc611 and mc275?

Thank you very much for such an awesome comment, very helpful.

What crossover Device would make sense absent the Infinity IRS Servo Control Unit Device which I'm not sure can be used separate with other speakers, although it does seem ideally configured.

It is true I am very concerned about 901 heat generation, and I'm surprised you have no problems with that even with your 9 foot ceiling and larger room. Not sure if you've ever measured watts used from the wall when 901s are at idle and in use, but I have learned these things use about 1000 W while both units are in use, which is consistent with a portable heating unit set to low being run continuously..  I find it challenging to understand how these Amps can be used without on going AC to offset the heat. 
 

I did see you updated your pictures,  the 901 Amps look very nice, and I have noted the racks as well which seem ideal.

I have considered a 1501, or 2 275s, to go along with my 611 amps but the convenience of the 901 would clearly do a better job to achieve the biamp goal.

@stephens770 so would something like this work as resister to match the gain on both amps?

https://www.sescom.com/products/view/product/productslug/sescom-ses-mkp-39-dual-channel-volume-control-with-dual-xlr-io

@w123ale Interesting little piece. Wish I would have found it years ago. Yes, one for each channel should work. Great if you have two balanced pre-outs per channel, use a good quality xlr splitter if you don't. Good luck!

Forgot to mention in post yesterday that I also used an Infinity RS crossover that worked well with my speakers that didn't have a servo or bass Eq. I believe it was designed for the 4.5's, but can use with any speakers. You can still find them used occasionally.